Smoking cessation and lung cancer outcomes: it is never too late to quit smoking

Although smokers often believe that it is too late to stop smoking, a pooled analysis from 35,481 lung cancer patients enrolled in the International Lung Cancer Consortium demonstrated clear survival benefits for recent quitters. The overall survival benefit that was obtained from smoking cessation was more pronounced in heavy smokers than in light smokers and increased upon a longer time since smoking cessation.

Introduction

After a lifetime of smoking, patients often have the feeling that it is too late to quit smoking since ‘the damage has already been done’. Addressing patients for smoking cessation during screening can be providential, as this is a teachable moment where health care professionals can reach out to a receptive patient with a heavy cumulative smoking history (more than 30 pack-years). A pooled analysis of the International Lung Cancer Consortium (ILCCO) aims to examine the survival benefits of quitting smoking, using the time since smoking cessation compared to current smoking at the time of lung cancer diagnosis.

For this analysis researchers used a pooled data set from the ILCCO database, including 17 lung cancer studies, conducted in North America, Europe and Asia and encompassed a total of 35,481 lung cancer patients. A pre-planned sensitivity analysis was performed to estimate lung cancer specific survival (13 studies) and mimic a high-risk population, with cumulative smoking history for more than 30 pack-years.

Results

Not surprisingly. adjusted Kaplan-Meier curves demonstrate that ‘never-smokers’ with lung cancer have a better overall survival (OS) rate than current smokers. In addition to this, former smokers have a slight benefit as compared to current smokers. Interestingly, a stepwise OS advantage was observed depending on the time since smoking cessation before lung cancer diagnosis. In fact, the OS benefit in patients who quit within two years before their lung cancer diagnosis was 12%, increasing to 16% in patients who quit 2-5 years before diagnosis and to 20% for patients who stopped smoking more than 5 years before they were diagnosed. All these differences proved to be significant (p< 0.001). In the subset of patients who smoked for more than 30 pack-years, the OS benefit was more pronounced than for those patients who smoked less than 30 pack-years (14% versus 5% for those patients that stopped within two years from diagnosis, 17% versus 14% for those who stopped between 2-5 years and 22% versus 16% for those patients that quitted smoking for more than five years before lung cancer diagnosis). This OS advantage was observed across all patient subsets, irrespective of sex, disease stage, histology and pack-years.

When addressing the lung cancer specific survival, in the population with available cause of death information (N=10,514), the pooled analysis demonstrated that patients who quitted smoking for more than five years before their diagnosis had a significant survival benefit of 15% (adjusted HR [95%CI]: 0.85 [0.78-0.92]) compared to current smokers at the time of lung cancer diagnosis. For patients who quitted between 2-5 years (adjusted HR [95%CI]: 0.93 [0.83-1.04]) or for less than 2 years before lung cancer diagnosis (adjusted HR [95%CI]: 0.95 [0.86-1.05]) a non-significant positive trend was observed.

Conclusion

Lung cancer patients who quit smoking show consistently higher survival rates compared to patients who continue smoking. Importantly, this also includes patients who stopped smoking within two years of their lung cancer diagnosis and was observed irrespective of other known prognostic factors. Among heavier smokers (more than 30 pack-years), the survival benefit of quitting is greater than among lighter smokers (less than 30 pack-years). The findings of this analysis provide supporting data that ‘it is never too late to quit smoking’. Smoking cessation can benefit current smokers, in a sense that quitting within a few years of a diagnosis of lung cancer is still associated with improved lung cancer survival, across all stages, histologies and pack-year categories.

Reference

Fares AF, Jiang M, Hung R, et al. Smoking cessation (CS) and lung cancer (LC) outcomes: A survival benefit for recent-quitters? A pooled analysis of 35,481 International Lung Cancer Consortium (ILCCO) patients. Presented at ASCO 2020; Abstract 1512.